Control device



Oct. 27, 1953 J. L. HARRIS 2,657,283

CONTRjD LKDEVICE Filed F-b, 3. 1 949 Patented Oct. 27, 1953 UNITEDSTATES PATENT OFFICE QQNTROL DEVIQE John L. Harris, Whitefish Bay, Wis.

Application February 23, 1949, Serial No. 77,860

8 Claims. 1

The present invention relates in general to a switching mechanism andmore particularly to switches adapted for use in timing apparatus.

One object of the invention is to provide a simple and positive drop offcam type switch mechanism in which a single cam is capable of providingan abrupt drop-01f action of its cam follower upon movement in onedirection and is also capable of lifting its cam follower upon movementin the opposite direction A further object of the invention is theprovision of a switching mechanism which is simple and positive inconstruction and which provides a plurality of switching operations in apredetermi ed q l Other objects of the invention will appear from thefollowing description and the appended claims.

For a full disclosure of the invention, reference is made to thefollowing detailed description and to the accompanying drawings inwhich:

Fig. l is an external front view of a timer embqsiv ne t in n o Fig 2 isa side View partly in section of the timer shown in Fig. 1;

Figs, 3, 4, 5 and 6 show the switch blades and cams in differentpositions assumed during operation;

Fig. 7 is a perspective view of a portion of the switch blade assembly;

Fig. 8 is an exploded view of the cam shaft assembly;

Fig. 9 is a perspective view showing the rear section of the cam shaft,and

Fig. 10 is a wiring diagram illustrating one application of theinvention.

Referring to Figs. 1 and 2, reference character I indicates a casesection to which are secured motor mounting studs 2 and 3 which supporta synchronous motor comprising a field core and coil assembly 4 and agear train barrel 5. Extending from the front of the gear train barreland through the front of the case is a final shaft 8 which carries a hubi. This hub is provided with a shoulder at its front end and carries adial 8 and an operating finger member 9. The dial 8 and finger member 9are pressed against the shoulder of the hub by a spring clip If]. Thisarrangement provides a slip friction drive for the dial and fingermember by the hub. It also provides a slipv frictional engagementbetween the dial and finger member so that these parts may be relativelyadjusted. The finger member is provided with a rearwardly extending pinI! and the dial is provided with a rearwardly extend- 2 ns Pin 12. Thefu io O he ns ill ap- P ar a thi de p on PZ C QS' Located inside thecase is a switch mounting plate 3- s l te may b secur d to h as by meansof screws l4 and spacers I5. The case and switch plate serve as bearingsfor a cam shaft [6, this shaft extending through the case and ca y ng ap int l which o e at he s it mechanism and indicates the position ofsuch mechanism.

Referring to Fig. 3 the switch mounting plate I3 carries a bracket I8which is generally U-shaped, having an outeturned blade carrying portionl9 and a lead terminal portion 20. This bracket carries a switch bladeor cam follower 2|, an intermediate switch blade 22 and an outer switchblade 23. As shown more clearly in Fig. 7, the cam follower blade isprovided with an offset portion 24 and an out-turned portion 25. Thisout-turned portion is provided with an opening 26 through which the endsof blades 22 and 23 extend. This provides a lost motion connectionbetween the cam follower blade and the switch blades. The switch blade23 carries a contact 2'! which cooperates with a stationary contact 28mounted on a bracket 29 which is similar to the bracket I 8. The switchblade 22 is adapted to engage a pin .30, which extends through themounting plate l3. The switch blade. 2| carries a contact 3! whichcooperates with a contact 32 carried by a cam follower 33 which ispivoted to the mounting plate at 34. This cam follower is biaseddownwardly by means of a U-shaped spring member 35 secured to a post 36carried by he m un n p a e.

Referring to Fig. 2, the cam shaft I6 is provided with a shoulder 37which bears against the inside of the case. This shaft is also providedwith a shoulder 38 bearing against the plate [3. A reduced portion 39 ofthe shaftextends into a hole in the plate [3. The cam shaft is thusmaintained between the case and the plate l3 by means of the twoshoulders. The cam shaft 16 also includes a reduced portion 49 providedwith a key- 4!. (This construction is shown more clearly in Fig. 9.) Thecam shaft supports cams 42 and 43. The cam 43 is provided with an opening 44 which fits tightly on the cam shaft. The cam 42 is provided withan opening 45 which fits loosely on the cam shaft, this opening having asection it which is considerably larger than the key 4| on the shaft.This arrangement provides a lost motion drive between the cam 42 and theshaft. It will be noted that the cam 42 is held in place on the shaftbetween the cam 43 55 and a shoulder M. In assembly, the cam 43 ispressed on the shaft so as to provide a slight clearance for the cam atso as to allow cam 2 to ride freel on the shaft.

The specific application of the embodiment of the invention shown is tocontrol a photographic enlarger and name printer. In this type of apparatus it is desired to operate the enlarger for periods of adjustableduration. Approximately 1% seconds before the enlarger is turned off thename printer should be turned on, the name printer and enlarger beingturned off simultaneously at the end of the timing period. Fig. 10 showsthe wiring diagram employed for obtaining this function. As shown inthis figure, the contact 28 is connected directly to one terminal of anappliance plug 43. The other side of the appliance plug is connected toa receptacle 49 for the enlarger, and also to an appliance receptacle dfor the name printer. This line is also con nected to one side of thetiming motor 5. The other side of the name printer receptacle 50 isconnected to the cam follower 33 while the other side of the enlargerreceptacle 49 is connected to the bracket is supporting the three switchblades. The pin 3!] is connected to the other side of the timing motor.The circuits for the various devices will be traced in the explanationof operation.

Operation With the parts in the positions shown in Figs. 1 and 3 thedevice is in the off position. At this time the pointer ll points to theword Off on. the front of the case. In this position contacts 21 and 28are open, the switch blade 22 is engaged with the pin 3d and thecontacts 3! and 32 are closed. For operating the device the operatorsets the finger member 9 on the dial for the timing desired. Theoperator then rotates the finger member in a clockwise direction untilthe pin ll strikes the shaft l6. As the pin approaches the shaft I6, itengages a cam section 5| on the pointer causing the pointer to revolvethe shaft [65 in a counterclockwise direction to the on position. Duringthe initial portion of the stroke the cam 22 remains stationary as thekey 4! on the shaft is not engaged with the end of opening 46 in thecam. However, the cam 43 is fixed on the shaft and revolves immediately.This cam is provided with a drop off section 52 which slips under thecam follower 33 as appears in Fig. l.

It will be noted that the cam 42 is provided with a raised portion 53and a recessed portion M which are joined by a sloping portion 55. Ascam 52 rotates counterclockwise, the inclined portion 55 engages the camfollower and causes it to move downwardly to the position shown in Fig.4 in which the contacts 21 and 28 are engaged. At this point, it shouldbe noted that switch blade 23 is biased, in the direction for holdingcontacts 2'l and 28 engaged. The cam follower blade, however than thebias of blade 22, and thus force greater than the bias of blade 22, andthus holds the contacts open when in the position shown in 3. However,when the cam follower is depressed as shown in Fig. 4 it releases blade22, permitting this blade to hold contacts 21 and 255 closed.

Preferably, the parts are proportioned so that on downward movement ofthe cam follower contacts 3! and 32 disengage before contacts 21 and 7.8engage. This prevents the name printer from flashing on and off duringthe off to on stroke of the cam shaft.

Summarizing the action in the off to on stroke, the cam 43 slips underthe cam follower 33 before the lost motion of cam 42 is taken up. Whenthe lost motion between cam 42 and the shaft is taken up, this camdrives the cam follower blade 4| downwardly, first breaking contacts 3|and 32 and then permitting contacts 21 and 28 to engage. The switchblade 22 remains engaged with the contact 30 during this entire portionof the stroke.

Referring to Fig. 10 it will be noted that closure of contacts 21 and 28energizes the enlarger receptacle 49. Power also passes from the blade23 through blade 22 and post 30 to the timing motor. The name printerreceptacle 50 is deenergized due to contacts 3| and 32 being open.

The timing motor now drives the dial and finger member in acounterclockwise direction. As the end of the timing period approaches,the pin 2 on the dial engages the upper extension 55 of the pointer andbegins to rotate the shaft IS in a clockwise direction. During theinitial portion of this clockwise stroke, the cam 42 remains stationaryas the lost motion between the cam and shaft in this direction has notbeen taken up. The cam 43, however, begins to rotate immediately and thedrop off 52 on this cam permits the cam follower to drop therebypermitting contacts 3| and 32 to engage. This stage of the cycle isshown in Fig. 5. Contacts 3| and 32 now energize the name printer. Asthe dial continues to rotate the cam shaft likewise continues to 1'0-tate, taking up the lost motion between the cam 42 and the shaft. Thecam then rotates until the cam follower rides down the sloping portion55 of the cam. Inasmuch as the lost motion drive now permits freerotation of the cam 42 in the clockwise direction, the cam snapsforwardly under the driving action of the cam follower, permitting thecam follower to reach the bottom section 54 of the cam. During thismovement the cam follower blade 2| pulls the switch blade 23 upwardly soas to break contacts 21 and 2B. This movement of the blade 3| also liftsthe cam follower 33 upwardly clear of the drop off section 52 of the cam44. This movement of cam follower 33 results from the bias of camfollower toward the cam being greater than that of cam follower 32. Theparts thus reassurne the positions shown in Fig. 3.

At times it is desirable to turn on the appli-- ance without having itturn off automatically. For example, when an enlarger is being focused,the time desired for this operation may be in excess of the maximumtiming provided by the timer. To obtain this result, the pointer isturned to Focus and the parts then assume the position shown in Fig. 6.In this position the cam 43 has rotated so that its enlarged portionElli has carried the cam follower blade 2| away from the cam 42 to aposition in which it presses the switch blade away from contact with thepin This breaks the timer motor circuit while maintaining the maincontacts 27 and 28 in closed position. The appliance thus remainsenergized until the pointer i1 is moved away from the focus position.

It should be noted that the pin 3|] cooperates with the cam 43 forlimiting rotation of the cam shaft. Thus the extension 56 of the camstrikes the pin (it for limiting the travel of the shaft in thecounterclockwise direction. The extension 5? of the cam 43 strikes thepin 30 'or lizigniting clockwise rotation of the shaft. (See Referringto Fig. 3, it should be noted that the free end of the cam follower ispositioned to one side of the cam shaft center so that the arc of travelof the free end of the cam follower is on an angle of about 45 with thearc of travel of the cam surfaces. With this arrangement the rotation ofthe cam has a direct lift component on the cam follower. This reducesthe friction between the cam and cam follower and permits the camfollower to operate the switch with a minimum of force.

From the foregoing description it will be apparent that the presentinvention provides the simple switch mechanism in which the switch maybe set by rotation of the shaft in one direction while still obtainingabrupt drop off action when the shaft is rotated in the oppositedirection to a predetermined point. It will be further apparent that theinvention provides a simple and positive sequence switching mechanism.While the invention has been described specifically as applied to anenlarger timer, the general principles of the invention are applicablefor many other uses. Also, many changes may be made in construction.without departing from the spirit and scope of the invention. It is,therefore, desired to be limited only by the scope of the appendedclaims.

What is claimed is:

1. In a switch construction, the combination of, a rotatable shaft, afirst cam loosely mounted on said shaft, lost motion drive means betweenthe first cam and said shaft, a second cam rigidly mounted on saidshaft, contact mechanism, a first cam follower arranged for actuation bysaid first cam for controlling said contact mechanism, and a second camfollower arranged for actuation by the said second cam for alsocontrolling said contact mechanism.

2. In a switch construction, the combination of, a rotatable shaft, afirst cam loosely mounted on the shaft, lost motion drive means betweenthe first cam and said shaft, a second cam mounted on the shaft,switching mean including first and second cam followers, the first camfollower riding the first cam on one side of the shaft and the secondcam follower riding the second cam on the opposite side of the shaft,both of the cam followers being biased toward the shaft and the firstcam follower being biased sufficiently to overcome the bias of thesecond cam follower, the first cam having a relatively high portion anda relatively low portion connected by a sloping portion arranged so thatthe first cam follower can ride from the low portion to the high portionas the cam is rotated in one direction by the shaft, the lost motiondrive means between the first cam and the shaft permitting snap movementof the cam when rotated in reverse direction by the shaft, said secondcam having an abrupt drop off, and means whereby snap movement of thefirst cam follower toward the shaft causes movement of the second camfollower away from the shaft sufllciently to clear said abrupt drop off.

3. In a switch construction, the combination of, a rotatable shaft, afirst cam loosely mounted on the shaft, lost motion drive means betweenthe first cam and said shaft, a second cam mounted on the shaft,switching means including a first set of contacts and a second set ofcontacts, a first cam follower riding the first cam on one side of thesame and arranged to control both sets of contacts, a second camfollower riding the second cam on the side of the shaft opposite saidfirst cam follower, said sec-- ond cam follower being arranged tocontrol one of said sets of contacts conjointly with the first camfollower, both of the carnfollowers being biased toward the shaft andthe first cam follower b-eing biased sufficiently to overcome the biasof the second cam follower, the first cam having a relatively highportion and a relatively low portion connected by a sloping portion arraged so that the first scam follower can ride from the low portion to thehigh portion as the cam is rotated in one direction by the shaft, thelost motion drive means between the fir t cam and the shaft permittingsnap movement of the cam when rotated in reverse direction by the shaft,said second cam having an abrupt drop off, and means whereby snapmovement of the first cam follower toward the shaft causes movement ofthe second cam follower away from the shaft sufficiently to clear saidabrupt drop off.

4. In a switch construction, an electric timing motor, a shaft arrangedto be rotated in one direction by the timing motor, manual means forrotating the shaft in the opposite direction, a cam freely supported bysaid shaft, a cam follower biased against the cam, a switch forcontrolling the timing motor comprising a stationary contact and aflexible switch blade biased toward said stationary contact and awayfrom the cam follower, a lost motion connection between the cam followerand switch blade, the bias of the cam follower being greater than thatof the switch blade whereby the cam follower on motion toward the camcauses the switch blade to disengage the stationary contact, lost motiondrive means between the cam and shaft, said cam having a relatively lowportion and a relatively high portion connected by a sloping portionarranged so that the cam follower can ride from the low portion to thehigh portion as the cam is rotated in one direction, said lost motiondrive means between the cam and shaft permitting snap movement of thecam when rotated in the reverse direction by the shaft, said snapmovement of the cam being caused by the bias of the cam follower actingon the sloping portion of the cam.

5. In a switch construction, an electric timing motor, a shaft arrangedto be rotated in one direction by the timing motor, manual means forrotating the shaft in the opposite direction, a

cam freely supported by said shaft, a first stationary contact, a firstflexible switch blade cooperating with said first stationary contact, asecond stationary contact, a second switch blade cooperating with thesecond stationary contact, a cam follower biased against the cam, lostmotion connecting means between the cam follower and said switch blades,lost motion drive means between the cam and shaft, said cam having arelatively low portion and a relatively high portion connected by asloping portion arranged so that the cam follower can ride from the lowportion to the high portion as the cam is rotated in one direction, saidlost motion drive means between the cam and shaft permitting snapmovement of the cam when rotated in the reverse direction by the shaft,said snap movement of the cam being caused by the bias of the'camfollower acting on the sloping portion of the cam.

6. In a switch construction, the combination of, a rotatable cam means,means for rotating said cam means in either direction, a first camfollower on one side of the cam means and biased against the same, asecond cam follower on the other side of the cam means and biasedagainst the cam means with a force greater than the first cam follower,contact means controlled by said cam followers, said cam means beingprovided with drop off portions arranged so that upon rotation of thecam means in one direction the first cam follower drops off and uponcontinued rotation of the cam means in the same direction the second camfollower drops off, means actuated by dropping off of the second camfollower for lifting the first cam follower clear of the cam means, andmeans for holding said cam follower in said clear position upon reversemovement of the cam means.

7. In a switch construction, a first stationary contact, a first switchblade biased against said first stationary contact, a second stationarycontact, a second switch blade biased against said second stationarycontact, said switch blades being biased in opposite directions, a cam,a cam follower biased against the cam with a force sufficient toovercome the bias of one of said switch blades, and 10st motionconnecting means be tween the cam follower and both of said switchblades.

8. In a switch construction, a first stationary contact, a first switchblade biased against said first stationary contact, a second stationarycontact, a second switch blade biased against said second stationarycontact, said switch blades being biased in opposite directions, a cam,a cam follower biased against the cam with a force sufficient toovercome the bias of one of said switch blades, lost motion connectingmeans between the cam follower and both of said switch blades, a secondcam arranged to operate said cam i01- lower, an actuator for both ofsaid cams, and lost motion drive means between one of said cams and saidactuator.

JOHN L. HARRIS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,831,605 Porter Nov. 10, 1931 2,274,635 Rhodes Mar. 3, 19422,521,301 Morrison Sept. 5, 1950 2,528,841 Morrison et a1. Nov. '7, 1950

